The invention involves a new process for the derivation of thiols, phenols, oxides, and primary and secondary amines in an aqueous solution for the purpose of quantitatively analyzing them under High Performance Liquid Chromatography (otherwise known as HPLC).
The present invention is related to processes for quantitatively analyzing mixtures including a compound bearing a nucleophilic group in a trace amount in an aqueous medium.
A particular application of the invention is the detection of traces of pollutants in aqueous or aqua organic environments.
The detection of pollutants is given in the present description as an example illustrating one of the applications of the invention.
The detection of numerous compounds present in trace amounts in aqueous or aqua organic environments is desirable in order to detect useful compounds, for which it is desired to determine their concentration or presence, or to detect contaminant compounds, also called, the xe2x80x9cmicro-pollutantsxe2x80x9d, which even in extremely low concentrations can have a negative impact on the environment and public health. Among these compounds, the detection and the quantification of carrier compounds of nucleophilic functions is particularly interesting, for example, phenols, oximes, thiols, amines.
The chemical industries among others, using compounds based on sulfur, phenols, oximes or amines, are naturally the important sources of these products. These elements can thus be present in the environment in the uncombined form, or in the precursor chemical compounds.
A significant source is created by pesticides. Certain pesticides in fact contain the nucleophilic functions cited above, in the uncombined or precursory form. When these functions are released by hydrolysis in the environment, they can lead to metabolites that are more toxic than the original pollutants.
The numerous molecules of biological interest (hormones, amino acids, neurotransmitters, etc.) are also carriers of these functions. These compounds are found in products of the agro-food industries and physiological liquids of living organisms.
In each of these cases, the quantitative analysis of these nucleophilic functions is desirable for reasons of medical diagnostics, the quality of the food, or the pollution index.
When their concentration is high (greater than 0.1 g/l), their quantitative analysis can be direct. Numerous methods are thus known in this area and are currently being used.
When their concentration is lower (typically less than a milligram per liter) and when a great precision of the quantitative analysis is necessary, the derivation of the nucleophilic functions that are sought after produces an effective solution to detect lower concentrations. The derivation consists in the creation of a covalent bond between the function studied and another chemical group for the purpose of forming a new entity that can be quantitatively analyzed by a traditional method. The increase of the detectability is linked to physiochemical properties of the deriving compound (increase of the molar extinction coefficient, increase of fluorescence, etc.).
Currently, the quantification and the identification of the chemical types present in trace amounts in a humid or aqueous environment is not easily realized as a rule, as far as the phenols, thiols, oximes are concerned. In this case, global methods can be resorted to which allow for example an estimation of the total concentration of phenols without it being possible to identify the different molecules present.
As far as the amines are concerned, several traditional methods for derivation are known. The chemical functions generally used in order to derive these amines in regard to their quantitative analysis are aldehydes, acid chlorides, acid anhydrides, carbamates (as a chemical function).
These methods have variable limits and disadvantages, such as low stability of the starting materials and derivatives obtained, specific reactivity to certain amines, the need for expensive material exclusively dedicated to these analyses.
In addition, no method exists for the simultaneous derivation applicable to all of the thiols, phenols, oximes, amines. U.S. Pat. No. 5,354,689 by Streicher describes a process that functions by using an excess of amines in order to look for traces of isocyanates, which is the opposite of the process according to the invention. Moreover, the process according to the US patent functions in an organic environment and not in an aqueous environment.
The patent CH 662 659 intends to quantitatively analyze the isocyanates which result from the manufacture of urethanes. The process according to the CH patent functions when dry.
The U.S. Pat. No. 3 891 670 Kanaoka describes a process that does not function with isocyanates. This patent does not involve amine functions.
The present invention corrects these shortcomings by providing a process for the derivation of compounds in a trace amount including a nucleophilic group in an aqueous medium for the purpose of quantitative analysis by traditional separative methods. The present invention provides a process for obtaining a urea or a carbamate entity by reaction of compounds having a nucleophilic group in an aqueous medium.
According to a second purpose of the invention, a simple device can be designed that uses this process and is economically fabricated.
Finally, according to a third purpose of the invention, the quantitative analysis can be performed on a very large range of compounds present in a humid environment in trace amounts.
The object of the present invention is the use of isocyanates to react to compounds having a nucleophilic group in an aqueous medium in which the nucleophilic groups can be, among others, phenols, thiols, oximes, and amines.
The very strong reactivity of isocyanates to water is known. However, it is totally unexpected to obtain an even stronger reactivity of the isocyanates to the nucleophilic groups. As such, there is a very unique reaction of compounds in a trace amount in a aqueous environment.
In the literature, there is a very strong prejudice against the use of isocyanates in an aqueous or aqua organic environment, due to their very strong reactivity (such as, xe2x80x9cOrganic Chemistryxe2x80x9d, 2nd Edition, Ray P. Brewster, 1953, pp 559, and in xe2x80x9cReactions of 1,3-Bis(2-chloroethy-1-nitrosourea and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea in Aqueous Solutionxe2x80x9d, Weinkam, Huey Shin Lin, Journal of Medicinal Chemistry, 1979, Vol. 22, No. 10, pp. 1193-1198). In fact, it is recommended to use only the isocyanates in solvents without water, or even traces of water.
In addition, the strong reactivity to water leads to storing them exclusively in an anhydrous environment, and to keep them in a dry place to preserve them.
The present invention obtains a completely unexpected effect which is the predominant reactivity of the isocyanates to the nucleophilic groups, even in the trace amounts, in an aqueous environment. As a result, it is possible to obtain a very simple and economical process for quantitative analysis based on this usage.
Nitrosourea is a masked, stable isocyanate which can act as an isocyanate reservoir because of its decomposition in an aqueous environment. The nitrosourea will decompose into an intermediate isocyanate and this intermediate isocyanate will react to the nucleophilic groups.
Nitrosoureas have the advantage of easily decomposing in molecular engineering, thus they are able to be conducted for the synthesis of very variable isocyanates suited to specific needs, contrary to the uncombined isocyanates whose manufacturing is delicate.
Nitrosourea is a precursor of isocyanates. This usage allows numerous industrial applications, one of which is the quantitative analysis of diverse functions, and also the creation of a quantitative analysis kit containing dry products that are very stable in storage and very inexpensive to manufacture.
The invention presented here also provides a process for the quantitative analysis of nucleophilic functions in an aqueous or aqua organic environment wherein it consists of the phases:
adding isocyanates to an aqueous solution having a basic pH containing the nucleophilic function to be quantitatively analyzed,
maintaining the solution over a duration of several minutes to several dozen minutes at a temperature less than 100xc2x0 C.,
quantitative analysis of carbamate, thiocarbamate or the urea obtained.
Quantitative analysis is an extensive industrial application of the use of the reactivity of isocyanates to nucleophilic groups in an aqueous environment.
As mentioned above, there is indeed a process for the quantitative analysis of the nucleophilic functions in spite of the fact that contrary to the recommendations for use, the isocyanates are used in an aqueous environment.
The duration of the quantitative analysis will be a function of the type of isocyanate used.
According to a specific claim, the process for quantitative analysis of nucleophilic functions is characterized in that the quantitative analysis of carbamate (R1xe2x80x94NHxe2x80x94COxe2x80x94XRxe2x80x2 with Xxe2x95x90O or ONxe2x95x90C), of thiocarbamate (R1xe2x80x94NHxe2x80x94COxe2x80x94SRxe2x80x2) or of the urea obtained (R1xe2x80x94NHxe2x80x94COxe2x80x94NHRxe2x80x2) is done by HPLC (High Performance Liquid Chromatography).
This device allows the use in the process of a detection by a separate traditional method.
The invention also is intended to include a device for quantitative analysis of nucleophilic functions in an aqueous or aqua organic environment, using a process according to the preceding claims.
A device of this type, a xe2x80x9cquantitative analysis kitxe2x80x9d allows the simple implementation of the process in various uses, with an easy and lasting storage of these reagents.